#include <stdio.h>
int main()
{
    //freopen("in.txt", "r", stdin);
    int h, w;
    while (scanf("%d %d", &h, &w) != EOF && !(h == 0 && w == 0))
    {
        for (int i = 0; i < h; i++)
        {
            for (int j = 0; j < w; j++)
            {
                if((i+j) % 2 == 0) printf("#");
                else printf(".");
            }
            printf("\n");
        }
        printf("\n");
    }
}